Liquid crystal alignment agent composition, method of producing liquid crystal alignment film using the same, and liquid crystal alignment film using the same

ABSTRACT

A liquid crystal alignment agent composition for producing a liquid crystal alignment film having enhanced alignment property and stability and a high voltage holding ratio, a method of producing a liquid crystal alignment film using the same, and a liquid crystal alignment film and a liquid crystal display device using the same, are provided.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a 35 U.S.C. 371 National Phase Entry Applicationfrom PCT/KR2018/011897, filed Oct. 10, 2018, which claims the benefit ofpriority from Korean Patent Application No. 10-2017-0136516 filed onOct. 20, 2017 with the Korean Intellectual Property Office, thedisclosures of which are incorporated herein by reference in theirentirety.

TECHNICAL FIELD

The present invention relates to a liquid crystal alignment agentcomposition for producing a liquid crystal alignment film havingenhanced liquid crystal alignment property and stability and a highvoltage holding ratio, a method of producing a liquid crystal alignmentfilm using the same, and a liquid crystal alignment film and a liquidcrystal display device using the same.

BACKGROUND ART

In a liquid crystal display device, a liquid crystal alignment filmplays a role in aligning liquid crystals in a predetermined direction.Specifically, the liquid crystal alignment film serves as a director inthe arrangement of liquid crystal molecules, and when the liquidcrystals move by an electric field to form an image, the liquid crystalalignment film helps the liquid crystals take an appropriate direction.In order to obtain uniform brightness and a high contrast ratio in aliquid crystal display device, it is essential for the liquid crystalsto be uniformly aligned.

As one of conventional methods of aligning liquid crystals, a rubbingmethod of applying a polymer film such as polyimide onto a substratesuch as glass, etc. and rubbing the surface thereof in a predetermineddirection with a fiber such as nylon or polyester has been used.However, in the rubbing method, when the fiber and the polymer film arerubbed, fine dust or electrical discharge (ESD) may occur, which maycause serious problems during production of a liquid crystal panel.

In order to solve the problems of the rubbing method, recent studieshave been conducted on a photo-alignment method in which anisotropy isinduced in the polymer film not through friction but through lightirradiation to align liquid crystals.

A variety of materials have been suggested as materials that may be usedin the photo-alignment method. Among them, a polyimide is mainly usedfor good performances of the liquid crystal alignment film. However, thepolyimide is generally poor in solvent solubility, and therefore it isdifficult to directly apply it in a process of forming an alignment filmby coating with a solution state of the polyimide. For this reason, aprecursor form such as a polyamic acid or a polyamic acid ester withexcellent solubility is coated and subjected to a high heat treatmentprocess to form the polyimide, which is then subjected to lightirradiation for alignment.

However, a lot of energy is required to obtain sufficient liquid crystalalignment by light irradiation of the polyimide film. Accordingly, thereare limitations that it is difficult to secure productivity in practiceand an additional heat treatment process is needed to obtain alignmentstability after light irradiation.

In addition, a high voltage holding ratio (VHR) is required forhigh-quality operation of a liquid crystal display device, but there isa limit to achieving the high voltage holding ratio by using thepolyimide alone. Particularly, in recent years, as a demand for a lowerpower display has increased, the liquid crystal alignment agent wasfound to affect not only basic properties such as the alignment propertyof liquid crystals, but also electrical properties such as an afterimagegenerated by a direct current/alternating voltage and the voltageholding ratio. Thus, there is a growing need for the development of aliquid crystal alignment material capable of simultaneously realizingexcellent liquid crystal alignment and electrical properties.

Accordingly, there is a need to develop a novel liquid crystal alignmentagent having excellent liquid crystal alignment and electricalproperties under high temperature environments to improve performance ofa liquid crystal display device and to realize a lower power display.

DETAILED DESCRIPTION OF THE INVENTION Technical Problem

The present invention provides a liquid crystal alignment agentcomposition having excellent alignment property and stability as well ashaving enhanced electrical properties such as a voltage holding ratiounder high temperature environments.

Further, the present invention provides a method of producing a liquidcrystal alignment film using the liquid crystal alignment agentcomposition.

Furthermore, the present invention provides a liquid crystal alignmentfilm produced by the production method and a liquid crystal displaydevice including the liquid crystal alignment film.

Technical Solution

The present invention provides a liquid crystal alignment agentcomposition including; a polymer for a first liquid crystal alignmentagent including two or more repeating units selected from the groupconsisting of a repeating unit represented by the following ChemicalFormula 1, a repeating unit represented by the following ChemicalFormula 2, and a repeating unit represented by the following ChemicalFormula 3, wherein the repeating unit represented by the followingChemical Formula 1 is included in an amount of 5 mol % to 74 mol % withrespect to a total of the repeating units represented by the followingChemical Formulae 1 to 3; and a polymer for a second liquid crystalalignment agent including one or more repeating units selected from thegroup consisting of a repeating unit represented by the followingChemical Formula 4, a repeating unit represented by the followingChemical Formula 5, and a repeating unit represented by the followingChemical Formula 6:

wherein, in Chemical Formulae 1 to 6,

R¹, R², R³, and R⁴ are each independently hydrogen or a C₁₋₁₀ alkyl,provided that R¹ and R² are not both hydrogen, and that R³ and R⁴ arenot both hydrogen,

X¹ is a tetravalent organic group represented by the following ChemicalFormula 7:

wherein, in Chemical Formula 7,

R⁵, R⁶, R⁷, and R⁸ are each independently hydrogen or a C₁₋₆ alkyl, and

X², X³, X⁴, X⁵, and X⁶ are each independently a tetravalent organicgroup derived from a hydrocarbon having 4 to 20 carbon atoms, or atetravalent organic group derived from a hydrocarbon having 4 to 20carbon atoms wherein one or more of H is substituted with a halogen orone or more of —CH₂— is substituted with —O—, —CO—, —S—, —SO—, —SO₂—, or—CONH— to prevent direct binding with oxygen or sulfur atoms in thetetravalent organic group, and

in Chemical Formulae 1 to 3,

Y¹ to Y³ are each independently a divalent organic group represented bythe following Chemical Formula 8:

wherein, in Chemical Formula 8,

R⁹ and R¹⁰ are each independently a halogen, a cyano, a C₁₋₁₀ alkyl, aC₂₋₁₀ alkenyl, a C₁₋₁₀ alkoxy, a C₁₋₁₀ fluoroalkyl, or a C₁₋₁₀fluoroalkoxy,

p and q are each independently an integer of 0 to 4,

L¹ is a single bond, —O—, —CO—, —S—, —SO₂—, —C(CH₃)₂—, —C(CF₃)₂—,—CONH—, —COO—, —(CH₂)_(z)—, —O(CH₂)_(z)O—, —O(CH₂)_(z)—,—OCH₂—C(CH₃)₂—CH₂O—, —COO—(CH₂)_(z)—OCO—, or —OCO—(CH₂)_(z)—COO—,wherein z is an integer of 1 to 10,

k and m are each independently an integer of 1 to 3, and

n is an integer of 0 to 3, and in Chemical Formulae 4 to 6,

Z¹, Z², and Z³ are each independently a divalent organic grouprepresented by the following Chemical Formula 9:

wherein, in Chemical Formula 9,

A¹ is an element of Group 15,

R¹¹ is hydrogen or a C₁₋₁₀ alkyl,

a is an integer of 1 to 3, and

A², A³, A⁴, and A⁵ are nitrogen or carbon, provided that at least one ofA² to A⁵ is nitrogen and the others are carbon.

Hereinafter, a liquid crystal alignment agent composition according to aspecific embodiment of the present invention, a method of producing aliquid crystal alignment film using the same, and a liquid crystaldisplay device including the liquid crystal alignment film thus producedwill be described in more detail.

Throughout the specification, when one part “includes” one constituentelement, unless otherwise specifically described, this does not meanthat another constituent element is excluded, but means that anotherconstituent element may be further included.

As used herein, the term “substituted” means that a hydrogen atom in acompound is changed to another substituent, and a position to besubstituted is not limited as long as the position is a position atwhich the hydrogen atom is substituted, that is, a position at which thesubstituent may be substituted, and when two or more are substituted,the two or more substituents may be the same as or different from eachother.

As used herein, the term “substituted or unsubstituted” means thatsubstitution is performed by one or more substituent groups selectedfrom the group consisting of deuterium; a halogen group; a cyano group;a nitro group; a hydroxyl group; a carbonyl group; an ester group; animide group; an amide group; an amino group; a carboxyl group; asulfonic acid group; a sulfonamide group; a phosphine oxide group; analkoxy group; an aryloxy group; an alkylthioxy group; an arylthioxygroup; an alkylsulfoxy group; an arylsulfoxy group; a silyl group; aboron group; an alkyl group; a cycloalkyl group; an alkenyl group; anaryl group; an aralkyl group; an aralkenyl group; an alkylaryl group; anarylphosphine group; or a heterocyclic group containing at least one ofN, O, and S atoms, or there is no substituent group, or substitution isperformed by a substituent group where two or more substituent groups ofthe exemplified substituent groups are linked, or there is nosubstituent group. For example, the term “substituent group where two ormore substituent groups are linked” may refer to a biphenyl group. Thatis, the biphenyl group may be an aryl group, or may be interpreted as asubstituent group where two phenyl groups are connected.

In the present specification,

or

means a bond connected to another substituent group, and a direct bondmeans a case where another atom does not exist in a portion representedby L¹ to L⁶.

In the present specification, the alkyl group may be straight-chained orbranched, and the number of carbon atoms thereof is not particularlylimited, but is preferably 1 to 10. According to another embodiment, thealkyl group has 1 to 6 carbon atoms. Specific examples of the alkylgroup include methyl, ethyl, propyl, n-propyl, isopropyl, butyl,n-butyl, isobutyl, tert-butyl, sec-butyl, 1-methyl-butyl, 1-ethyl-butyl,pentyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, hexyl, n-hexyl,1-methylpentyl, 2-methylpentyl, 4-methyl-2-pentyl, 3,3-dimethylbutyl,2-ethylbutyl, heptyl, n-heptyl, 1-methylhexyl, cyclopentylmethyl,cycloheptylmethyl, octyl, n-octyl, tert-octyl, 1-methylheptyl,2-ethylhexyl, 2-propylpentyl, n-nonyl, 2,2-dimethylheptyl,1-ethyl-propyl, 1,1-dimethyl-propyl, isohexyl, 2-methylpentyl,4-methylhexyl, 5-methylhexyl, and the like, but are not limited thereto.

The fluoroalkyl group having 1 to 10 carbon atoms may be one in which atleast one hydrogen atom in an alkyl group having 1 to 10 carbon atoms issubstituted with fluorine, and the fluoroalkoxy group having 1 to 10carbon atoms may be one in which at least one hydrogen atom in an alkoxygroup having 1 to 10 carbon atoms is substituted with fluorine.

The halogen group may be fluorine (F), chlorine (Cl), bromine (Br), oriodine (I).

The element of Group 15 may be nitrogen (N), phosphorus (P), arsenic(As), antimony (Sb), or bismuth (Bi).

The nitrogen oxide is a compound in which a nitrogen atom and an oxygenatom are bonded, and the nitrogen oxide functional group means afunctional group containing a nitrogen oxide in the functional group.Examples of the nitrogen oxide functional group include a nitro group(—NO₂) and the like.

The liquid crystal alignment agent composition according to the presentinvention is characterized by including both of a polymer for a firstliquid crystal alignment agent which is a partially imidized polyimideprecursor and a polymer for a second liquid crystal alignment agentwhich is a polyimide precursor derived from diamine of an asymmetricpyridine structure.

When the polyimide is conventionally used as a liquid crystal alignmentfilm, a polyimide precursor, a polyamic acid, or a polyamic acid esterhaving excellent solubility is coated and dried to form a coating film,and then converted to polyimide through a high-temperature heattreatment process, which is then subjected to light irradiation foralignment treatment. However, a lot of light irradiation energy isrequired to obtain sufficient liquid crystal alignment by lightirradiation of the polyimide film, and an additional heat treatmentprocess is also required to secure alignment stability after lightirradiation. The use of a lot of light irradiation energy and theadditional high-temperature heat treatment process are verydisadvantageous in terms of process cost and time, and thus there arerestrictions in application of the method to a practical mass-productionprocess.

Accordingly, the present inventors found that when the polymer for thefirst liquid crystal alignment agent including two or more repeatingunits of Chemical Formulae 1 to 3 prepared from a reaction productcontaining an imide group-containing diamine compound having a specificstructure is used, imide repeating units that have been already imidizedare included in a predetermined amount, and thus anisotropy is directlygenerated by light irradiation without the high-temperature heattreatment process after formation of the coating film, and subsequently,heat treatment is performed to complete an alignment film. Accordingly,light irradiation energy may be greatly reduced, and a liquid crystalalignment film having an enhanced alignment property and stability maybe produced even by a simple process including a single heat treatmentprocess.

Further, the present inventors found that when the polymer for thesecond liquid crystal alignment agent including one or more repeatingunits of Chemical Formulae 4 to 6 prepared from a reaction productcontaining a nitrogen-atom containing diamine compound having a specificstructure, in addition to the polymer for the first liquid crystalalignment agent, are included in a liquid crystal alignment agentcomposition, a liquid crystal alignment film produced therefrom may havea high voltage holding ratio even at a high temperature, a reduction incontrast ratio or an afterimage phenomenon may be improved, andalignment stability due to heat stress and mechanical strength of thealignment film may be improved.

According to one embodiment of the present invention, a liquid crystalalignment agent composition including the polymer for the first liquidcrystal alignment agent including two or more repeating units selectedfrom the group consisting of the repeating unit represented by ChemicalFormula 1, the repeating unit represented by Chemical Formula 2, and therepeating unit represented by Chemical Formula 3, wherein the repeatingunit represented by Chemical Formula 1 is included in an amount of 5 mol% to 74 mol %, with respect to a total of the repeating unitsrepresented by Chemical Formulae 1 to 3; and the polymer for the secondliquid crystal alignment agent including one or more repeating unitsselected from the group consisting of the repeating unit represented byChemical Formula 4, the repeating unit represented by Chemical Formula5, and the repeating unit represented by Chemical Formula 6, isprovided.

Specifically, with regard to the polymer for the first liquid crystalalignment agent and the polymer for the second liquid crystal alignmentagent in the liquid crystal alignment agent composition according to oneembodiment, in the repeating units of Chemical Formulae 1 to 6, X¹ is atetravalent organic group represented by Chemical Formula 7, and X², X³,X⁴, X⁵, and X⁶ are each independently a tetravalent organic groupderived from a hydrocarbon having 4 to 20 carbon atoms, or a tetravalentorganic group derived from a hydrocarbon having 4 to 20 carbon atomswherein one or more of H is substituted with a halogen or one or more of—CH₂— is substituted with —O—, —CO—, —S—, —SO—, —SO₂—, or —CONH— toprevent direct binding with oxygen or sulfur atoms in the tetravalentorganic group.

For example, X², X³, X⁴, X⁵, and X⁶ may each independently be atetravalent organic group represented by the following Chemical Formula10:

wherein, in Chemical Formula 10,

R⁵, R⁶, R⁷, and R⁸ are each independently hydrogen or a C₁₋₆ alkyl,

R¹² and R¹³ are each independently hydrogen or a C₁₋₁₀ alkyl,

L² is any one selected from the group consisting of a single bond, —O—,—CO—, —S—, —SO—, —SO₂—, —CR¹⁴R¹⁵—, —CONH—, —COO—, —(CH₂)_(b)—,—O(CH₂)_(b)O—, —COO—(CH₂)_(b)—OCO—, —HN—(CH₂)_(b)—NH—,—R¹⁴N—(CH₂)_(b)—NR¹⁵—, phenylene, and combinations thereof, wherein R¹⁴and R¹⁵ are each independently hydrogen, a C₁₋₁₀ alkyl, or a C₁₋₁₀fluoroalkyl, and each b is independently an integer of 1 to 10.

Further, the polymer for the first liquid crystal alignment agent in theliquid crystal alignment agent composition according to one embodimentmay include the repeating units of Chemical Formulae 1 to 3 wherein Y¹,Y², and Y³ may each independently be a divalent organic grouprepresented by Chemical Formula 8.

In Chemical Formula 8, hydrogen is bound to carbon which is notsubstituted with R⁹ or R¹⁰, and when p or q is an integer of 2 to 4, aplurality of R⁹ or R¹⁰ may be the same or different substituents.Further, in Chemical Formula 8, k and m may each independently be aninteger of 0 to 3, or 1 to 3, and n may be an integer of 0 to 3, or 0 or1.

Chemical Formula 8 corresponds to a part of the repeating unit derivedfrom the imide-containing diamine having a specific structure which is aprecursor used in the formation of the polymer for the liquid crystalalignment agent.

More specifically, Chemical Formula 8 may be the following Chemical

Formula 11 or Chemical Formula 12:

wherein, in Chemical Formula 12, L³ is a single bond, —O—, —SO₂—, or—CR¹⁶R¹⁷—, wherein R¹⁶ and R¹⁷ are each independently hydrogen or aC₁₋₁₀ alkyl.

Preferably, Chemical Formula 11 may be the following Chemical Formula11-1:

Further, the Chemical Formula 12 may be the following Chemical Formula12-1:

wherein, in Chemical Formula 12-1, L³ is O or CH₂.

Further, the polymer for the second liquid crystal alignment agent inthe liquid crystal alignment agent composition according to oneembodiment may have repeating units of Chemical Formulae 4 to 6, whereinZ¹, Z², and Z³ may each independently be a divalent organic grouprepresented by Chemical Formula 9. The Z¹, Z², and Z³ may be defined asthe divalent organic group represented by Chemical Formula 4 to providea polymer for a liquid crystal alignment agent having variousstructures, which may exhibit the above-descried effects.

In Chemical Formula 9, A¹ may be an element of Group 15, and the elementof Groups 15 may be nitrogen (N), phosphorus (P), arsenic (As), antimony(Sb), or bismuth (Bi). The R¹¹ is a functional group binding to A¹, andmay bind to the A¹ element by a number represented by a. Preferably, inChemical Formula 9, A¹ may be nitrogen, R¹¹ may be hydrogen, and a maybe 1.

On the other hand, by satisfying the condition that in Chemical Formula9, at least one of A² to A⁵ is nitrogen and the others are carbon,Chemical Formula 9 may form an asymmetric structure which does not formsymmetry with respect to the center point or the center line due to thenitrogen atom. Chemical Formula 9 is a repeating unit derived from anitrogen atom-containing diamine having a specific structure, which is aprecursor used for the formation of the polymer for the liquid crystalalignment agent, and this is considered to be due to the use of anasymmetric diamine as described later.

The functional group represented by Chemical Formula 9 has a structuralfeature in which two aromatic cyclic compounds, preferably, aheteroaromatic cyclic compound and an aromatic cyclic compound, arebound through a secondary amine group or a tertiary amine group.Therefore, the liquid crystal alignment agent may satisfy an equivalentlevel or more of alignment property or afterimage property and may havean improved voltage holding ratio, thereby realizing excellentelectrical properties.

On the other hand, when two aromatic cyclic compounds are bound by asingle bond without a secondary amine group or a tertiary amine group,there are technical problems in that the alignment property of theliquid crystal alignment agent becomes poor, and the voltage holdingratio is relatively reduced.

Further, in the case where neither of the two aromatic cyclic compoundsbound through a secondary amine group or a tertiary amine group containa nitrogen atom, even if the imidization reaction of the polyamic acidor the polyamic acid ester formed by the reaction of amine and acidanhydride proceeds (e.g., via 230° C. heat treatment), a sufficientimidization reaction does not proceed, and thus there is a limitation inthat an imidization rate decreases within the final liquid crystalalignment film.

Further, the functional group represented by Chemical Formula 11 ischaracterized in that only the amine group and hydrogen are bound toeach of two aromatic cyclic compounds, preferably, the heteroaromaticcyclic compound and the aromatic cyclic compound, and other substituentsare not introduced. When a substituent such as a fluoroalkyl group isintroduced into the heteroaromatic cyclic compound or the aromaticcyclic compound, there is a technical problem in that the alignmentproperty deteriorates due to the substituent.

More specifically, in Chemical Formula 9, one of A² to A⁵ may benitrogen and the others may be carbon. In Chemical Formula 9, one of A²and A⁵ is nitrogen and the other is carbon, and A³ and A⁴ may be carbon.That is, in Chemical Formula 9, the aromatic ring containing A² to A⁵may have a pyridine structure. Accordingly, the liquid crystal displaydevice to which the polymer for the liquid crystal alignment agent ofone embodiment is applied may realize a high voltage holding ratio andliquid crystal alignment property.

Further, Chemical Formula 9 may include one or more repeating unitsselected from the group consisting of the following Chemical Formula9-1, Chemical Formula 9-2, and Chemical Formula 9-3:

wherein, in Chemical Formula 9-1, Chemical Formula 9-2, and ChemicalFormula 9-3, descriptions of A¹, A², A³, A⁴, A⁵, R¹¹ and a include theabove description of Chemical Formula 9.

As described above, since the repeating unit of Chemical Formula 9includes one or more repeating units selected from the group consistingof Chemical Formula 9-1, Chemical Formula 9-2, and Chemical Formula 9-3,a much better liquid crystal alignment property may be realized.

The polymer for the first liquid crystal alignment agent in the liquidcrystal alignment agent composition according to one embodiment mayinclude the repeating unit represented by Chemical Formula 1 which is animide repeating unit, among the repeating units represented by ChemicalFormula 1, Chemical Formula 2, and Chemical Formula 3, in an amount of 5mol % to 74 mol %, and preferably 10 mol % to 60 mol %, with respect toa total of the repeating units.

As described above, when the polymer including the specific amount ofthe imide repeating unit represented by Chemical Formula 1 is used, thepolymer for the first liquid crystal alignment agent includes apredetermined amount of already imidized imide repeating units, and thusa liquid crystal alignment film having excellent alignment property andstability may be produced even when the high-temperature heat treatmentprocess is omitted and light is directly irradiated.

If the repeating unit represented by Chemical Formula 1 is included atless than the above-mentioned content range, sufficient alignmentproperties may not be exhibited and alignment stability may bedeteriorated. If the content of the repeating unit represented byChemical Formula 1 exceeds the above-mentioned content range, there is aproblem in that the solubility is lowered and thus it is difficult toprepare a stable alignment solution capable of coating. Accordingly, itis preferable to include the repeating unit represented by ChemicalFormula 1 within the above-mentioned content range, in terms ofproviding a polymer for a liquid crystal alignment agent havingexcellent storage stability, electrical properties, alignmentproperties, and alignment stability.

Further, the repeating unit represented by Chemical Formula 2 or therepeating unit represented by Chemical Formula 3 may be included in anappropriate amount depending on the desired properties.

Specifically, the repeating unit represented by Chemical Formula 2 maybe included in an amount of 0 mol % to 40 mol %, preferably 0 mol % to30 mol %, with respect to a total of the repeating units represented byChemical Formulas 1 to 3. The repeating unit represented by ChemicalFormula 2 has a low rate of conversion to imide during ahigh-temperature heat treatment process after light irradiation, andtherefore, if the amount exceeds the above range, the overallimidization rate is insufficient, thereby deteriorating the alignmentstability. Accordingly, the repeating unit represented by ChemicalFormula 2 exhibits appropriate solubility within the above-mentionedrange, thereby providing a polymer for a liquid crystal alignment agentwhich may implement a high imidization rate while having excellentprocessing properties.

Furthermore, the repeating unit represented by Chemical Formula 3 may beincluded in an amount of 0 mol % to 95 mol %, and preferably 10 mol % to90 mol %, with respect to a total of the repeating units represented byChemical Formulae 1 to 3. Within such a range, excellent coatingproperties may be exhibited, thereby providing a polymer for a liquidcrystal alignment agent which may implement a high imidization ratewhile having excellent processing properties.

Meanwhile, the polymer for the second liquid crystal alignment agent inthe liquid crystal alignment agent composition according to oneembodiment may include the repeating unit represented by ChemicalFormula 4 which is an imide repeating unit, among the repeating unitsrepresented by Chemical Formula 4, Chemical Formula 5, and ChemicalFormula 6, in an amount of 0 mol % to 80 mol %, and preferably 0.1 mol %to 65 mol %, with respect to a total of the repeating units.

As described above, when the polymer including the specific amount ofthe imide repeating unit represented by Chemical Formula 4 is used, thepolymer includes a predetermined amount of already imidized imiderepeating units, and thus a liquid crystal alignment film havingexcellent alignment property and stability may be produced even when thehigh-temperature heat treatment process is omitted and light is directlyirradiated.

If the repeating unit represented by Chemical Formula 4 is included atless than the above-mentioned content range, sufficient alignmentproperties may not be exhibited and alignment stability may bedeteriorated. If the content of the repeating unit represented byChemical Formula 4 exceeds the above-mentioned content range, there is aproblem in that the solubility is lowered and thus it is difficult toprepare a stable alignment solution capable of coating. Accordingly, itis preferable to include the repeating unit represented by ChemicalFormula 4 within the above-mentioned content range, in terms ofproviding a polymer for a liquid crystal alignment agent havingexcellent storage stability, electrical properties, alignmentproperties, and alignment stability.

Further, the repeating unit represented by Chemical Formula 5 or therepeating unit represented by Chemical Formula 6 may be included in anappropriate amount depending on the desired properties.

Specifically, the repeating unit represented by Chemical Formula 5 maybe included in an amount of 0 mol % to 50 mol %, preferably 0.1 mol % to30 mol %, with respect to a total of the repeating units represented byChemical Formulae 4 to 6. The repeating unit represented by ChemicalFormula 5 has a low rate of conversion to imide during ahigh-temperature heat treatment process after light irradiation, andtherefore, if the amount exceeds the above range, the overallimidization rate is insufficient, thereby deteriorating the alignmentstability. Accordingly, the repeating unit represented by ChemicalFormula 5 exhibits appropriate solubility within the above-mentionedrange, thereby providing a polymer for a liquid crystal alignment agentwhich may implement a high imidization rate while having excellentprocessing properties.

Furthermore, the repeating unit represented by Chemical Formula 6 may beincluded in an amount of 10 mol % to 100 mol %, and preferably 30 mol %to 99.8 mol %, with respect to a total of the repeating unitsrepresented by Chemical Formulae 4 to 6. Within such a range, excellentcoating properties may be exhibited, thereby providing a polymer for aliquid crystal alignment agent which may implement a high imidizationrate while having excellent processing properties.

Meanwhile, the liquid crystal alignment agent composition according toone embodiment may include the polymer for the first liquid crystalalignment agent and the polymer for the second liquid crystal alignmentagent at a weight ratio of about 5:95 to about 95:5, and preferablyabout 15:85 to about 85:15.

As described above, the polymer for the first liquid crystal alignmentagent may include a predetermined amount of already imidized imiderepeating units, and thus anisotropy is directly generated by lightirradiation without the high-temperature heat treatment process afterformation of the coating film, and subsequently, heat treatment isperformed to complete an alignment film. In addition, the polymer forthe second liquid crystal alignment agent may include the repeating unitderived from a nitrogen atom-containing diamine compound having aspecific asymmetric structure, and thus a high voltage holding ratio maybe obtained even at a high temperature, and a reduction in a contrastratio or an afterimage phenomenon may be improved, thereby improvingelectrical properties. When the polymer for the first liquid crystalalignment agent and the polymer for the second liquid crystal alignmentagent, each having the above-described characteristics, are used afterbeing mixed with each other in the above weight ratio, excellentphotoreactive property and liquid crystal alignment property of thepolymer for the first liquid crystal alignment agent and the excellentelectrical properties of the polymer for the second liquid crystalalignment agent may complement each other, and therefore, excellentcoating properties may be exhibited, thereby producing a liquid crystalalignment film which may implement a high imidization rate while havingexcellent processing properties, and may have excellent electricalproperties such as an afterimage generated by the directcurrent/alternating voltage and the voltage holding ratio, and a liquidcrystal alignment film which may have a much better alignment propertyand electrical properties at the same time.

Meanwhile, the polymer for the second liquid crystal alignment agent inthe liquid crystal alignment agent composition according to oneembodiment may further include one or more repeating units selected fromthe group consisting of a repeating unit represented by the followingChemical Formula 13, a repeating unit represented by the followingChemical Formula 14, and a repeating unit represented by the followingChemical Formula 15:

wherein, in Chemical Formulae 13 to 15,

at least one of R¹⁸ and R¹⁹ is an alkyl group having 1 to 10 carbonatoms and the other is hydrogen,

X⁷ to X⁹ are each independently a tetravalent organic group, and

Z⁴ to Z⁶ are each independently a divalent organic group represented bythe following Chemical Formula 16:

wherein, in Chemical Formula 16,

R²⁰ and R²¹ are each independently a halogen, a cyano, a C₁₋₁₀ alkyl, aC₂₋₁₀ alkenyl, a C₁₋₁₀ alkoxy, a C₁₋₁₀ fluoroalkyl, or a C₁₋₁₀fluoroalkoxy,

p′ and q′ are each independently an integer of 0 to 4,

L⁴ is a single bond, —O—, —CO—, —S—, —SO₂—, —C(CH₃)₂—, —C(CF₃)₂—,—CONH—, —COO—, —(CH₂)_(z)—, —O(CH₂)_(z)O—, —O(CH₂)_(z)—,—OCH₂—C(CH₃)₂—CH₂O—, —COO—(CH₂)_(z)—OCO—, or —OCO—(CH₂)_(z)—COO—,wherein each z is independently an integer of 1 to 10,

k′ and m′ are each independently an integer of 0 to 3, and

n′ is an integer of 0 to 3.

In Chemical Formula 16, hydrogen may be bound to carbon which is notsubstituted with R²⁰ or R²¹, and p′ and q′ are each independently aninteger of 0 to 4, 1 to 4, or 2 to 4, and when p′ or q′ is an integer of2 to 4, a plurality of R²⁰ or R²¹ may be the same or differentsubstituents.

Further, in Chemical Formula 16, k′ and m′ may each independently be aninteger of 0 to 3, or 1 to 3, and n′ may be an integer of 0 to 3, or 1to 3.

More specifically, Chemical Formula 16 may be the following ChemicalFormula 17 or Chemical Formula 18:

wherein, in Chemical Formula 18,

L⁵ is a single bond, —O—, —SO₂—, or —CR²²R²³—, wherein R²² and R²³ areeach independently hydrogen or a C₁₋₁₀ alkyl.

Preferably, the Chemical Formula 17 may be the following ChemicalFormula 17-1:

Further, the Chemical Formula 18 may be the following Chemical Formula18-1:

wherein, in Chemical Formula 18-1, L⁵ is O or CH₂.

In Chemical Formulae 13 to 15, X⁷ to X⁹ are each independently atetravalent organic group derived from a hydrocarbon having 4 to 20carbon atoms, or a tetravalent organic group derived from a hydrocarbonhaving 4 to 20 carbon atoms wherein one or more of H is substituted witha halogen or one or more of —CH₂— is substituted with —O—, —CO—, —S—,—SO—, —SO₂—, or —CONH— to prevent direct binding with oxygen or sulfuratoms in the tetravalent organic group.

For example, X⁷ to X⁹ may each independently include a tetravalentorganic group described in the following Chemical Formula 19:

wherein, in Chemical Formula 19,

R²⁴, R²⁵, R²⁶, and R²⁷ are each independently hydrogen or a C₁₋₆ alkyl,

R²⁸ and R²⁹ are each independently hydrogen or a C₁₋₁₀ alkyl, and

L⁶ is any one selected from the group consisting of a single bond, —O—,—CO—, —S—, —SO—, —SO₂—, —CR³⁰R³¹—, —COO—, —(CH₂)_(b)—, —O(CH₂)_(b)O—,—COO—(CH₂)_(b)—OCO—, —HN—(CH₂)_(b)—NH—, —R³⁰N—(CH₂)_(b)—NR³¹—,phenylene, and combinations thereof, wherein R³⁰ and R³¹ are eachindependently hydrogen, a C₁₋₁₀ alkyl, or a C₁₋₁₀ fluoroalkyl, and eachb is independently an integer of 1 to 10.

In this regard, a molar ratio between one or more repeating unitsselected from the group consisting of the repeating unit represented byChemical Formula 4, the repeating unit represented by Chemical Formula5, and the repeating unit represented by Chemical Formula 6, and one ormore repeating units selected from the group consisting of the repeatingunit represented by Chemical Formula 13, the repeating unit representedby Chemical Formula 14, and the repeating unit represented by ChemicalFormula 15, may be 1:100 to 100:1.

Further, the polymer for the first liquid crystal alignment agent andthe polymer for the second liquid crystal alignment agent may have aweight average molecular weight of 1000 g/mol to 200,000 g/mol. Theweight average molecular weight means a weight average molecular weightin terms of polystyrene measured by a GPC method. In the process ofdetermining the weight average molecular weight in terms of polystyrenemeasured by the GPC method, a commonly known analyzing device, adetector such as a refractive index detector or a UV-detector, and ananalytical column may be used. Commonly applied conditions fortemperature, solvent, and flow rate may be used. Specific examples ofthe measurement conditions may include a temperature of 40° C., a mixedsolvent of dimethylformamide (DMF)/tetrahydrofuran (THF), and a flowrate of 0.5 mL/min to 1.0 mL/min.

On the other hand, according to still another embodiment of the presentinvention, a method of producing a liquid crystal alignment film usingthe liquid crystal alignment agent composition as described above isprovided. The method of producing a liquid crystal alignment film mayinclude the steps of: coating the liquid crystal alignment agentcomposition onto a substrate to form a coating film (step 1); drying thecoating film (step 2); irradiating the coating film with lightimmediately after the drying step to perform an alignment treatment(step 3); and heat-treating and curing the alignment-treated coatingfilm (step 4).

The step 1 is a step of coating the above-described liquid crystalalignment agent composition onto a substrate to form a coating film.

The method of coating the liquid crystal alignment agent compositiononto a substrate is not particularly limited, and for example, a methodsuch as screen printing, offset printing, flexographic printing, inkjetprinting, etc. may be used.

Furthermore, the liquid crystal alignment agent composition may be thosewhich are dissolved or dispersed in an organic solvent. Specificexamples of the organic solvent include N,N-dimethylformamide,N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-methylcaprolactam,2-pyrrolidone, N-ethylpyrrolidone, N-vinylpyrrolidone, dimethylsulfoxide, tetramethylurea, pyridine, dimethyl sulfone, hexamethylsulfoxide, γ-butyrolactone, 3-methoxy-N,N-dimethylpropanamide,3-ethoxy-N,N-dimethylpropanamide, 3-butoxy-N,N-dimethylpropanamide,1,3-dimethyl-imidazolidinone, ethyl amyl ketone, methyl nonyl ketone,methyl ethyl ketone, methyl isoamyl ketone, methyl isopropyl ketone,cyclohexanone, ethylene carbonate, propylene carbonate, diglyme,4-hydroxy-4-methyl-2-pentanone, ethylene glycol monomethyl ether,ethylene glycol monomethyl ether acetate, ethylene glycol monoethylether, ethylene glycol monoethyl ether acetate, ethylene glycolmonopropyl ether, ethylene glycol monopropyl ether acetate, ethyleneglycol monoisopropyl ether, ethylene glycol monoisopropyl ether acetate,ethylene glycol monobutyl ether, ethylene glycol monobutyl etheracetate, and the like. These solvents may be used alone or in a mixturethereof.

In addition, the liquid crystal alignment agent composition may furtherinclude other components in addition to the organic solvent. For anon-limiting example, when the liquid crystal alignment agentcomposition has been coated, an additive capable of improving uniformityof film thickness or surface smoothness, improving adhesion between theliquid crystal alignment film and the substrate, changing the dielectricconstant and conductivity of a liquid crystal alignment film, orincreasing the density of the liquid crystal alignment film, may furtherbe included. Such an additive may be exemplified by a variety ofsolvents, surfactants, silane-based compounds, dielectric substances,crosslinkable compounds, etc.

The step 2 is a step of drying the coating film which is formed bycoating the liquid crystal alignment agent composition onto a substrate.

In the step of drying the coating film, a method such as heating of acoating film or vacuum evaporation may be used, and the drying may bepreferably carried out at 50° C. to 150° C., or at 60° C. to 140° C.

The step 3 is a step of irradiating the coating film with lightimmediately after the drying step to perform alignment treatment.

In the present disclosure, the “irradiating the coating film immediatelyafter the drying step” means that light is directly irradiated, afterthe drying step, without carrying out a heat treatment at a temperatureequal to or higher than that of the drying step, and steps other thanthe heat treatment may be added.

More specifically, when a liquid crystal alignment film is producedusing a conventional liquid crystal alignment agent including a polyamicacid or a polyamic acid ester, a step of irradiating light afteressentially performing a high-temperature heat treatment for imidizationof the polyamic acid is included. However, when a liquid crystalalignment film is produced using the liquid crystal alignment agent ofone embodiment described above, the heat treatment step is not included,and light is directly irradiated to perform alignment treatment, andthen the alignment-treated coating film is cured by a heat treatment,thereby producing a liquid crystal alignment film having sufficientalignment property and enhanced stability with a low light irradiationenergy.

In the alignment treatment step, the light irradiation is performed byirradiating polarized ultraviolet rays having a wavelength of 150 nm to450 nm. In this case, the intensity of the light exposure may varydepending on the kind of the polymer for the liquid crystal alignmentagent. Preferably, energy of 10 mJ/cm² to 10 J/cm², and more preferably,energy of 30 mJ/cm² to 2 J/cm², may be irradiated.

As for the ultraviolet rays, polarized ultraviolet rays selected amongultraviolet rays subjected to polarization treatment by a method ofpassing through or reflecting with {circle around (1)} a polarizingdevice using a substrate in which a dielectric anisotropic material iscoated on the surface of a transparent substrate such as quartz glass,soda lime glass, soda lime-free glass, etc., {circle around (2)} apolarizer plate on which aluminum or metal wires are finely deposited,or {circle around (3)} a Brewster's polarizing device operating by thereflection of quartz glass, etc., are irradiated to perform thealignment treatment. In this regard, the polarized ultraviolet rays maybe irradiated perpendicularly to the surface of the substrate, or may beirradiated by directing at an angle of incidence toward a specificangle. By this method, the alignment ability of the liquid crystalmolecules is imparted to the coating film.

The step 4 is a step of heat-treating and curing the alignment-treatedcoating film.

The step of heat-treating and curing the alignment-treated coating filmis a step that is carried out after light irradiation even in theconventional method of producing a liquid crystal alignment film using apolymer for a liquid crystal alignment agent including a polyamic acidor a polyamic acid ester, and is distinguished from the heat treatmentstep which is performed to imidize the liquid crystal alignment agentbefore irradiating light or while irradiating light, after coating theliquid crystal alignment agent onto a substrate.

In this regard, the heat treatment may be carried out by a heating meanssuch as a hot plate, a hot air circulation path, an infrared rayfurnace, and the like, and the heat treatment is preferably carried outat a temperature of 150° C. to 300° C., or 200° C. to 250° C.

On the other hand, after the step of drying the coating film (step 2), astep of heat-treating the coating film immediately after the drying stepat a temperature equal to or higher than that of the drying step may befurther included, if necessary. The heat treatment may be performed by aheating means such as a hot plate, a hot air circulation path, aninfrared furnace, or the like, and is preferably performed at 150° C. to250° C. In this process, the liquid crystal alignment agent may beimidized.

That is, the method of producing a liquid crystal alignment film mayinclude the steps of: coating the above-mentioned liquid crystalalignment agent onto a substrate to form a coating film (step 1); dryingthe coating film (step 2); heat-treating the coating film immediatelyafter the drying step at a temperature equal to or higher than that ofthe drying step (step 3); irradiating the heat-treated coating film withlight or rubbing the coating film to perform alignment treatment (step4); and heat-treating and curing the alignment-treated coating film(step 5).

On the other hand, according to still another embodiment of the presentinvention, a liquid crystal alignment film produced by theabove-described method of producing the liquid crystal alignment film isprovided.

As described above, when the polymer for the first liquid crystalalignment agent including two or more repeating units selected from thegroup consisting of the repeating unit represented by Chemical Formula1, the repeating unit represented by Chemical Formula 2, and therepeating unit represented by Chemical Formula 3, wherein the imiderepeating unit represented by Chemical Formula 1, among the repeatingunits, is included in an amount of 5 mol % to 74 mol %, and the polymerfor the second liquid crystal alignment agent including one or morerepeating units selected from the group consisting of the repeating unitrepresented by Chemical

Formula 4, the repeating unit represented by Chemical Formula 5, and therepeating unit represented by Chemical Formula 6 are mixed and used, itis possible to produce a liquid crystal alignment film having enhancedalignment property and stability.

On the other hand, according to still another embodiment of the presentinvention, a liquid crystal display device including the liquid crystalalignment film described above is provided.

The liquid crystal alignment film may be introduced into a liquidcrystal cell by a known method, and likewise, the liquid crystal cellmay be introduced into a liquid crystal display device by a knownmethod. The liquid crystal alignment film may be produced from thepolymer including the particular amount of the repeating unitrepresented by Chemical Formula 1, and thus may implement excellentstability together with excellent physical properties. Accordingly, itis possible to provide a liquid crystal display device having highreliability.

Advantageous Effects

According to the present invention, a method of producing a liquidcrystal alignment film having excellent alignment property andstability, a high voltage holding ratio at a high temperature, andexcellent electrical properties by improving deterioration of a contrastratio or an afterimage phenomenon through a simple process with alowered light irradiation energy, the method capable of providing theliquid crystal alignment film by applying a liquid crystal alignmentagent composition onto a substrate, drying the coating film, immediatelyirradiating the coating film with light to perform an alignmenttreatment while omitting a high-temperature heat treatment process, andthen heat-treating and curing the alignment-treated coating film; aliquid crystal alignment film produced thereby; and a liquid crystaldisplay device including the liquid crystal alignment film, areprovided.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present invention will be described in more detail in the followingexamples. However, the following examples are for illustrative purposesonly, and the scope of the present invention is not intended to belimited thereby.

PREPARATION EXAMPLE Preparation Example 1: Preparation of Diamine DA1-1

Preparation was performed as in the following reaction scheme.

Specifically, CBDA (cyclobutane-1,2,3,4-tetracarboxylic dianhydride,compound 1) and 4-nitroaniline were dissolved in DMF (dimethylformamide)to prepare a mixture. Subsequently, this mixture was allowed to react atabout 80° C. for about 12 hours to prepare an amic acid of a compound 2.Thereafter, the amic acid was dissolved in DMF, and acetic anhydride andsodium acetate were added thereto to prepare a mixture. Subsequently,the amic acid in the mixture was subjected to imidization at about 90°C. for about 4 hours to prepare a compound 3. An imide of the compound 3thus prepared was dissolved in DMAc (dimethylacetamide), and then Pd/Cwas added thereto to prepare a mixture. This mixture was reduced atabout 45° C. under hydrogen pressure of about 6 bar for about 20 hoursto prepare a diamine DA1-1.

Preparation Example 2: Preparation of Diamine DA1-2

DA1-2 was prepared in the same manner as in Preparation Example 1,except that DMCBDA (1,3-dimethylcyclobutane-1,2,3,4-tetracarboxylicdianhydride) was used instead of CBDA(cyclobutane-1,2,3,4-tetracarboxylic dianhydride).

Preparation Example 3: Synthesis of Diamine DA1-3

Preparation was performed as in the following reaction scheme.

Specifically, 25 g of CBDA (cyclobutane-1,2,3,4-tetracarboxylicdianhydride, compound 1) was added to 250 mL of methanol, and 1 to 2drops of hydrochloric acid was added thereto, and heated under reflux atabout 75° C. for about 5 hours. The solvent was removed under reducedpressure, and 300 mL of ethyl acetate and n-hexane were added forsolidification. A produced solid was filtered under reduced pressure anddried under reduced pressure at about 40° C. to obtain 32 g of acompound 4.

100 mL of toluene was added to 34 g of the obtained compound 4, and 35 gof oxalyl chloride was added dropwise at room temperature. 2 to 3 dropsof dimethylformamide (DMF) was added dropwise and stirred at about 50°C. for about 16 hours. After cooling to room temperature, the solventand remaining oxalyl chloride were removed under reduced pressure. 300mL of n-hexane was added to a yellow solid product and heated underreflux at about 80° C. The heated reaction solution was filtered toremove impurities which were not dissolved in n-hexane, and slowlycooled to room temperature. A produced white crystal was filtered andthen dried in a vacuum oven at about 40° C. to obtain 32.6 g of acompound 5.

29.6 g of 4-nitroaniline and 21.7 g of triethanolamine (TEA) were addedto about 400 mL of tetrahydrofuran (THF), and 32.6 g of compound 5 wasadded thereto at room temperature. After stirring at room temperaturefor about 16 hours, a produced precipitate was filtered. About 400 ml ofdichloromethane was added to a filtrate, followed by washing with a 0.1N hydrochloric acid aqueous solution and then washing with a saturatedsodium hydrogen carbonate (NaHCO₃) aqueous solution. The washed organicsolution was filtered under reduced pressure to obtain a solid product.The product was recrystallized from dichloromethane to obtain 43 g of asolid-phase dinitro compound 6.

43 g of the dinitro compound 6 thus obtained was put in a high-pressurereactor and dissolved in about 500 mL of THF. 2.2 g of 10 wt % Pd/C wasadded thereto, followed by stirring under hydrogen gas (H₂) at 3 atm forabout 16 hours at room temperature. After reaction, Pd—C was removedusing a Celite filter. After filtration, a filtrate was concentratedunder reduced pressure to obtain 37 g of esterified diamine DA1-3.

Preparation Example 4: Synthesis of Diamine DA2-1

18.3 g (100 mmol) of 2-chloro-5-nitropyridine (compound 7) and 12.5 g(98.6 mmol) of para-phenylenediamine (p-PDA, compound 8) were completelydissolved in about 200 mL of dimethyl sulfoxide (DMSO), and then 23.4 g(200 mmol) of trimethylamine (TEA) was added thereto, and stirred atroom temperature for about 12 hours. When the reaction was completed,the reaction product was put in a container containing about 500 mL ofwater, followed by stirring for about 1 hour. A solid obtained byfiltration was washed with about 200 mL of water and about 200 mL ofethanol to obtain 16 g (61.3 mmol) of a compound 9 (yield: 60%).

The compound 9 was dissolved in about 200 mL of a 1:1 mixture of ethylacetate (EA) and THF, and then 0.8 g of palladium/carbon (Pd/C) wasadded, followed by stirring under a hydrogen atmosphere for about 12hours. After completion of the reaction, a filtrate filtered through aCelite pad was concentrated to obtain 11 g of a diamine compound DA2-1(pIDA) (yield: 89%).

Preparation Example 5: Synthesis of Diamine DA2-2

A diamine compound DA2-2 was prepared in the same manner as inPreparation Example 4, except that meta-phenylenediamine (m-PDA) wasused instead of para-phenylenediamine (p-PDA, compound 8).

Preparation Example 6: Synthesis of Diamine DA2-3

A diamine compound DA2-3 was prepared in the same manner as inPreparation Example 4, except that 2-chloro-4-nitropyridine was usedinstead of 2-chloro-5-nitropyridine (compound 7).

Synthesis Example Synthesis Examples 1 to 4 and Comparative SynthesisExample 1: Synthesis of First Polymer Synthesis Example 1: Preparationof Polymer P-1 for Liquid Crystal Alignment Agent

5.0 g (13.3 mmol) of DA1-1 prepared in Preparation Example 1 wascompletely dissolved in 71.27 g of anhydrous N-methyl pyrrolidone (NMP).In an ice bath, 2.92 g (13.03 mmol) of1,3-dimethyl-cyclobutane-1,2,3,4-tetracarboxylic dianhydride (DMCBDA)was added to the solution, and stirred at room temperature for about 16hours to prepare a polymer P-1 for a liquid crystal alignment agent.

A molecular weight of the polymer P-1 was confirmed by GPC, and as aresult, its number average molecular weight (Mn) was 15,500 g/mol andits weight average molecular weight (Mw) was 31,000 g/mol. A monomerstructure of the polymer P-1 is determined by an equivalent ratio of theused monomer, and in the molecule, a ratio of the imide structure was50.5%, and a ratio of the amic acid structure was 49.5%.

Synthesis Example 2: Preparation of Polymer P-2 for Liquid CrystalAlignment Agent

5.376 g of DA1-2 prepared in Preparation Example 2 was first dissolvedin 74.66 g of NMP, and 2.92 g of1,3-dimethyl-cyclobutane-1,2,3,4-tetracarboxylic dianhydride (DMCBDA)was added thereto, and stirred at room temperature for about 16 hours.Thereafter, a polymer P-2 was prepared in the same manner as inSynthesis Example 1.

A molecular weight of the polymer P-2 was confirmed by GPC, and as aresult, its number average molecular weight (Mn) was 17,300 g/mol andits weight average molecular weight (Mw) was 34,000 g/mol. In themolecule of the polymer P-2, a ratio of the imide structure was 50.5%,and a ratio of the amic acid structure was 49.5%.

Synthesis Example 3: Preparation of Polymer P-3 for Liquid CrystalAlignment Agent

5.0 g of DA1-2 prepared in Preparation Example 2 and 1.07 g ofp-phenylenediamine were first dissolved in 89.81 g of NMP, and 1.90 g ofcyclobutane-1,2,3,4-tetracarboxylic dianhydride (CBDA) and 3.00 g ofoxydiphthalic dianhydride were added thereto, and stirred at roomtemperature for about 16 hours to prepare a polymer P-3.

A molecular weight of the polymer P-3 was confirmed by GPC, and as aresult, its number average molecular weight (Mn) was 17,000 g/mol andits weight average molecular weight (Mw) was 33,000 g/mol. In themolecule of the polymer P-3, a ratio of the imide structure was 33.8%,and a ratio of the amic acid structure was 66.2%.

Synthesis Example 4: Preparation of Polymer P-4 for Liquid CrystalAlignment Agent

5.0 g of DA1-1 prepared in Preparation Example 2 and 3.93 g of DA1-3prepared in Preparation Example 3 were first dissolved in 127.94 g ofNMP, and then 5.28 g of cyclobutane-1,2,3,4-tetracarboxylic dianhydride(CBDA) was added thereto, and stirred for about 16 hours at roomtemperature to prepare a polymer P-4 for a liquid crystal alignmentagent.

Comparative Synthesis Example 1: Preparation of Polymer PR-1 for LiquidCrystal Alignment Agent

6.00 g of p-phenylenediamine was first dissolved in 156.9 g of NMP, and5.34 g of cyclobutane-1,2,3,4-tetracarboxylic dianhydride (CBDA) and6.10 g of 1,3-dimethyl-cyclobutane-1,2,3,4-tetracarboxylic dianhydride(DMCBDA) were added thereto, and stirred for about 16 hours at roomtemperature to prepare a polymer PR-1.

A molecular weight of the polymer PR-1 was confirmed by GPC, and as aresult, its number average molecular weight (Mn) was 15,000 g/mol andits weight average molecular weight (Mw) was 28,000 g/mol. The monomerstructure of the polymer PR-1 was analyzed, and as a result, a ratio ofthe amic acid structure in the molecule was 100%.

Synthesis Examples 5 to 25 and Comparative Synthesis Examples 2 to 7:Synthesis of Second Polymer Synthesis Example 5: Polymer Q-1 for LiquidCrystal Alignment Agent

19.743 g (0.099 mmol) of diamine DA2-1 prepared in Preparation Example 4was completely dissolved in 225.213 g of anhydrous N-methyl pyrrolidone(NMP).

In an ice bath, 20.0 g (0.092 mmol) of pyromellitic dianhydride (PMDA)was added to the solution, and stirred at room temperature for about 16hours to prepare a polymer Q-1 for a liquid crystal alignment agent. Amolecular weight of the polymer Q-1 was confirmed by GPC, and as aresult, its weight average molecular weight (Mw) was 27,000 g/mol.

Synthesis Example 6: Polymer Q-2 for Liquid Crystal Alignment Agent

14.637 g (0.073 mmol) of diamine DA2-1 prepared in Preparation Example 4was completely dissolved in 225.213 g of anhydrous N-methyl pyrrolidone(NMP).

In an ice bath, 20.0 g (0.068 mmol) of 3,3′,4,4′-biphenyltetracarboxylic acid dianhydride (BPDA) was added to the solution, andstirred at room temperature for about 16 hours to prepare a polymer Q-2for a liquid crystal alignment agent. A molecular weight of the polymerQ-2 was confirmed by GPC, and as a result, its weight average molecularweight (Mw) was 24,000 g/mol.

Synthesis Example 7: Polymer Q-3 for Liquid Crystal Alignment Agent

19.211 g (0.096 mmol) of diamine DA2-1 prepared in Preparation Example 4was completely dissolved in 222.194 g of anhydrous N-methyl pyrrolidone(NMP).

In an ice bath, 20.0 g (0.089 mmol) of1,2,4,5-cyclohexanetetracarboxylic dianhydride (HPMDA) was added to thesolution, and stirred at room temperature for about 16 hours to preparea polymer Q-3 for a liquid crystal alignment agent. A molecular weightof the polymer Q-3 was confirmed by GPC, and as a result, its weightaverage molecular weight (Mw) was 26,500 g/mol.

Synthesis Example 8: Polymer Q-4 for Liquid Crystal Alignment Agent

1.974 g (0.01 mmol) of diamine DA2-1 prepared in Preparation Example 4and 9.596 g (0.089 mmol) of p-phenylenediamine (p-PDA) were completelydissolved in 178.897 g of anhydrous N-methyl pyrrolidone (NMP).

In an ice bath, 20.0 g (0.092 mmol) of pyromellitic dianhydride (PMDA)was added to the solution, and stirred at room temperature for about 16hours to prepare a polymer Q-4 for a liquid crystal alignment agent. Amolecular weight of the polymer Q-4 was confirmed by GPC, and as aresult, its weight average molecular weight (Mw) was 24,500 g/mol.

Synthesis Example 9: Polymer Q-5 for Liquid Crystal Alignment Agent

9.872 g (0.049 mmol) of diamine DA2-1 prepared in Preparation Example 4and 5.331 g (0.049 mmol) of p-phenylenediamine (p-PDA) were completelydissolved in 199.482 g of anhydrous N-methyl pyrrolidone (NMP).

In an ice bath, 20.0 g (0.092 mmol) of pyromellitic dianhydride (PMDA)was added to the solution, and stirred at room temperature for about 16hours to prepare a polymer Q-5 for a liquid crystal alignment agent. Amolecular weight of the polymer Q-5 was confirmed by GPC, and as aresult, its weight average molecular weight (Mw) was 27,500 g/mol.

Synthesis Example 10: Polymer Q-6 for Liquid Crystal Alignment Agent

1.974 g (0.01 mmol) of diamine DA2-1 prepared in Preparation Example 4and 17.768 g (0.089 mmol) of 4,4′-oxydianiline (ODA) were completelydissolved in 225.208 g of anhydrous N-methyl pyrrolidone (NMP).

In an ice bath, 20.0 g (0.092 mmol) of pyromellitic dianhydride (PMDA)was added to the solution, and stirred at room temperature for about 16hours to prepare a polymer Q-6 for a liquid crystal alignment agent. Amolecular weight of the polymer Q-6 was confirmed by GPC, and as aresult, its weight average molecular weight (Mw) was 28,500 g/mol.

Synthesis Example 11: Polymer Q-7 for Liquid Crystal Alignment Agent

9.872 g (0.049 mmol) of diamine DA2-1 prepared in Preparation Example 4and 9.871 g (0.049 mmol) of 4,4′-oxydianiline (ODA) were completelydissolved in 225.21 g of anhydrous N-methyl pyrrolidone (NMP).

In an ice bath, 20.0 g (0.092 mmol) of pyromellitic dianhydride (PMDA)was added to the solution, and stirred at room temperature for about 16hours to prepare a polymer Q-7 for a liquid crystal alignment agent. Amolecular weight of the polymer Q-7 was confirmed by GPC, and as aresult, its weight average molecular weight (Mw) was 27,000 g/mol.

Synthesis Example 12: Polymer Q-8 for Liquid Crystal Alignment Agent

1.974 g (0.01 mmol) of diamine DA2-1 prepared in Preparation Example 4and 17.593 g (0.089 mmol) of 4,4′-methylenedianiline (MDA) werecompletely dissolved in 224.218 g of anhydrous N-methyl pyrrolidone(NMP).

In an ice bath, 20.0 g (0.092 mmol) of pyromellitic dianhydride (PMDA)was added to the solution, and stirred at room temperature for about 16hours to prepare a polymer Q-8 for a liquid crystal alignment agent. Amolecular weight of the polymer Q-8 was confirmed by GPC, and as aresult, its weight average molecular weight (Mw) was 29,500 g/mol.

Synthesis Example 13: Polymer Q-9 for Liquid Crystal Alignment Agent

9.872 g (0.049 mmol) of diamine DA2-1 prepared in Preparation Example 4and 9.774 g (0.049 mmol) of 4,4′-methylenedianiline (MDA) werecompletely dissolved in 224.66 g of anhydrous N-methyl pyrrolidone(NMP).

In an ice bath, 20.0 g (0.092 mmol) of pyromellitic dianhydride (PMDA)was added to the solution, and stirred at room temperature for about 16hours to prepare a polymer Q-9 for a liquid crystal alignment agent. Amolecular weight of the polymer Q-9 was confirmed by GPC, and as aresult, its weight average molecular weight (Mw) was 28,000 g/mol.

Synthesis Example 14: Polymer Q-10 for Liquid Crystal Alignment Agent

1.464 g (0.007 mmol) of diamine DA2-1 prepared in Preparation Example 4and 7.114 g (0.066 mmol) of p-phenylenediamine (p-PDA) were completelydissolved in 161.939 g of anhydrous N-methyl pyrrolidone (NMP).

In an ice bath, 20.0 g (0.068 mmol) of 3,3′,4,4′-biphenyltetracarboxylic acid dianhydride (BPDA) was added to the solution, andstirred at room temperature for about 16 hours to prepare a polymer Q-10for a liquid crystal alignment agent. A molecular weight of the polymerQ-10 was confirmed by GPC, and as a result, its weight average molecularweight (Mw) was 27,500 g/mol.

Synthesis Example 15: Polymer Q-11 for Liquid Crystal Alignment Agent

1.464 g (0.007 mmol) of diamine DA2-1 prepared in Preparation Example 4and 13.172 g (0.066 mmol) of 4,4′-oxydianiline (ODA) were completelydissolved in 196.272 g of anhydrous N-methyl pyrrolidone (NMP).

In an ice bath, 20.0 g (0.068 mmol) of 3,3′,4,4′-biphenyltetracarboxylic acid dianhydride (BPDA) was added to the solution, andstirred at room temperature for about 16 hours to prepare a polymer Q-11for a liquid crystal alignment agent. A molecular weight of the polymerQ-11 was confirmed by GPC, and as a result, its weight average molecularweight (Mw) was 25,500 g/mol.

Synthesis Example 16: Polymer Q-12 for Liquid Crystal Alignment Agent

1.464 g (0.007 mmol) of diamine DA2-1 prepared in Preparation Example 4and 13.043 g (0.066 mmol) of 4,4′-methylenedianiline (MDA) werecompletely dissolved in 195.537 g of anhydrous N-methyl pyrrolidone(NMP).

In an ice bath, 20.0 g (0.068 mmol) of 3,3′,4,4′-biphenyltetracarboxylic acid dianhydride (BPDA) was added to the solution, andstirred at room temperature for about 16 hours to prepare a polymer Q-12for a liquid crystal alignment agent. A molecular weight of the polymerQ-12 was confirmed by GPC, and as a result, its weight average molecularweight (Mw) was 27,000 g/mol.

Synthesis Example 17: Polymer Q-13 for Liquid Crystal Alignment Agent

1.921 g (0.01 mmol) of diamine DA2-1 prepared in Preparation Example 4and 9.337 g (0.086 mmol) of p-phenylenediamine (p-PDA) were completelydissolved in 177.128 g of anhydrous N-methyl pyrrolidone (NMP).

In an ice bath, 20.0 g (0.089 mmol) of1,2,4,5-cyclohexanetetracarboxylic dianhydride (HPMDA) was added to thesolution, and stirred at room temperature for about 16 hours to preparea polymer Q-13 for a liquid crystal alignment agent. A molecular weightof the polymer Q-13 was confirmed by GPC, and as a result, its weightaverage molecular weight (Mw) was 23,500 g/mol.

Synthesis Example 18: Polymer Q-14 for Liquid Crystal Alignment Agent

1.921 g (0.01 mmol) of diamine DA2-1 prepared in Preparation Example 4and 17.289 g (0.086 mmol) of 4,4′-oxydianiline (ODA) were completelydissolved in 222.189 g of anhydrous N-methyl pyrrolidone (NMP).

In an ice bath, 20.0 g (0.089 mmol) of1,2,4,5-cyclohexanetetracarboxylic dianhydride (HPMDA) was added to thesolution, and stirred at room temperature for about 16 hours to preparea polymer Q-14 for a liquid crystal alignment agent. A molecular weightof the polymer Q-14 was confirmed by GPC, and as a result, its weightaverage molecular weight (Mw) was 26,500 g/mol.

Synthesis Example 19: Polymer Q-15 for Liquid Crystal Alignment Agent

1.921 g (0.01 mmol) of diamine DA2-1 prepared in Preparation Example 4and 17.119 g (0.086 mmol) of 4,4′-methylenedianiline (MDA) werecompletely dissolved in 177.128 g of anhydrous N-methyl pyrrolidone(NMP).

In an ice bath, 20.0 g (0.089 mmol) of1,2,4,5-cyclohexanetetracarboxylic dianhydride (HPMDA) was added to thesolution, and stirred at room temperature for about 16 hours to preparea polymer Q-15 for a liquid crystal alignment agent. A molecular weightof the polymer Q-15 was confirmed by GPC, and as a result, its weightaverage molecular weight (Mw) was 25,000 g/mol.

Synthesis Example 20: Polymer Q-16 for Liquid Crystal Alignment Agent

1.974 g (0.01 mmol) of diamine DA2-2 prepared in Preparation Example 5and 9.596 g (0.089 mmol) of p-phenylenediamine (p-PDA) were completelydissolved in 178.897 g of anhydrous N-methyl pyrrolidone (NMP).

In an ice bath, 20.0 g (0.092 mmol) of pyromellitic dianhydride (PMDA)was added to the solution, and stirred at room temperature for about 16hours to prepare a polymer Q-16 for a liquid crystal alignment agent. Amolecular weight of the polymer Q-16 was confirmed by GPC, and as aresult, its weight average molecular weight (Mw) was 22,500 g/mol.

Synthesis Example 21: Polymer Q-17 for Liquid Crystal Alignment Agent

1.974 g (0.01 mmol) of diamine DA2-2 prepared in Preparation Example 5and 17.768 g (0.089 mmol) of 4,4′-oxydianiline (ODA) were completelydissolved in 225.208 g of anhydrous N-methyl pyrrolidone (NMP).

In an ice bath, 20.0 g (0.092 mmol) of pyromellitic dianhydride (PMDA)was added to the solution, and stirred at room temperature for about 16hours to prepare a polymer Q-17 for a liquid crystal alignment agent. Amolecular weight of the polymer Q-17 was confirmed by GPC, and as aresult, its weight average molecular weight (Mw) was 24,500 g/mol.

Synthesis Example 22: Polymer Q-18 for Liquid Crystal Alignment Agent

1.974 g (0.01 mmol) of diamine DA2-2 prepared in Preparation Example 5and 17.593 g (0.089 mmol) of 4,4′-methylenedianiline (MDA) werecompletely dissolved in 224.218 g of anhydrous N-methyl pyrrolidone(NMP).

In an ice bath, 20.0 g (0.092 mmol) of pyromellitic dianhydride (PMDA)was added to the solution, and stirred at room temperature for about 16hours to prepare a polymer Q-18 for a liquid crystal alignment agent. Amolecular weight of the polymer Q-18 was confirmed by GPC, and as aresult, its weight average molecular weight (Mw) was 23,000 g/mol.

Synthesis Example 23: Polymer Q-19 for Liquid Crystal Alignment Agent

1.974 g (0.01 mmol) of diamine DA2-3 prepared in Preparation Example 6and 9.596 g (0.089 mmol) of p-phenylenediamine (p-PDA) were completelydissolved in 178.897 g of anhydrous N-methyl pyrrolidone (NMP).

In an ice bath, 20.0 g (0.092 mmol) of pyromellitic dianhydride (PMDA)was added to the solution, and stirred at room temperature for about 16hours to prepare a polymer Q-19 for a liquid crystal alignment agent. Amolecular weight of the polymer Q-19 was confirmed by GPC, and as aresult, its weight average molecular weight (Mw) was 21,500 g/mol.

Synthesis Example 24: Polymer Q-20 for Liquid Crystal Alignment Agent

1.974 g (0.01 mmol) of diamine DA2-3 prepared in Preparation Example 6and 17.768 g (0.089 mmol) of 4,4′-oxydianiline (ODA) were completelydissolved in 225.208 g of anhydrous N-methyl pyrrolidone (NMP).

In an ice bath, 20.0 g (0.092 mmol) of pyromellitic dianhydride (PMDA)was added to the solution, and stirred at room temperature for about 16hours to prepare a polymer Q-20 for a liquid crystal alignment agent. Amolecular weight of the polymer Q-20 was confirmed by GPC, and as aresult, its weight average molecular weight (Mw) was 24,500 g/mol.

Synthesis Example 25: Polymer Q-21 for Liquid Crystal Alignment Agent

1.974 g (0.01 mmol) of diamine DA2-3 prepared in Preparation Example 6and 17.593 g (0.089 mmol) of 4,4′-methylenedianiline (MDA) werecompletely dissolved in 224.218 g of anhydrous N-methyl pyrrolidone(NMP).

In an ice bath, 20.0 g (0.092 mmol) of pyromellitic dianhydride (PMDA)was added to the solution, and stirred at room temperature for about 16hours to prepare a polymer Q-21 for a liquid crystal alignment agent. Amolecular weight of the polymer Q-21 was confirmed by GPC, and as aresult, its weight average molecular weight (Mw) was 21,000 g/mol.

Comparative Synthesis Example 2: Polymer QR-1 for Liquid CrystalAlignment Agent

26.852 g (0.099 mmol) of p-phenylenediamine (p-PDA) was completelydissolved in 265.496 g of anhydrous N-methyl pyrrolidone (NMP).

In an ice bath, 20.0 g (0.092 mmol) of pyromellitic dianhydride (PMDA)was added to the solution, and stirred at room temperature for about 16hours to prepare a polymer QR-1 for a liquid crystal alignment agent. Amolecular weight of the polymer QR-1 was confirmed by GPC, and as aresult, its weight average molecular weight (Mw) was 26,000 g/mol.

Comparative Synthesis Example 3: Polymer QR-2 for Liquid CrystalAlignment Agent

19.743 g (0.099 mmol) of 4,4′-oxydianiline (ODA) was completelydissolved in 225.208 g of anhydrous N-methyl pyrrolidone (NMP).

In an ice bath, 20.0 g (0.092 mmol) of pyromellitic dianhydride (PMDA)was added to the solution, and stirred at room temperature for about 16hours to prepare a polymer QR-2 for a liquid crystal alignment agent. Amolecular weight of the polymer QR-2 was confirmed by GPC, and as aresult, its weight average molecular weight (Mw) was 21,000 g/mol.

Comparative Synthesis Example 4: Polymer QR-3 for Liquid CrystalAlignment Agent

19.548 g (0.089 mmol) of 4,4′-methylenedianiline (MDA) was completelydissolved in 224.218 g of anhydrous N-methyl pyrrolidone (NMP).

In an ice bath, 20.0 g (0.092 mmol) of pyromellitic dianhydride (PMDA)was added to the solution, and stirred at room temperature for about 16hours to prepare a polymer QR-3 for a liquid crystal alignment agent. Amolecular weight of the polymer QR-3 was confirmed by GPC, and as aresult, its weight average molecular weight (Mw) was 23,000 g/mol.

Comparative Synthesis Example 5: Polymer S-1 for Liquid CrystalAlignment Agent

A polymer S-1 for a liquid crystal alignment agent was prepared in thesame manner as in Synthesis Example 5, except that6-(4-aminophenyl)pyridin-3-amine represented by the following ChemicalFormula A was used instead of diamine DA2-1 prepared in PreparationExample 4.

Comparative Synthesis Example 6: Polymer S-2 for Liquid CrystalAlignment Agent

A polymer S-2 for a liquid crystal alignment agent was prepared in thesame manner as in Synthesis Example 5, except that4,4′-diaminodiphenylamine represented by the following Chemical FormulaB was used instead of diamine DA2-1 prepared in Preparation Example 4.

Comparative Synthesis Example 7: Polymer S-3 for Liquid CrystalAlignment Agent

A polymer S-3 for a liquid crystal alignment agent was prepared in thesame manner as in Synthesis Example 5, except thatN-(2,6-bis(trifluoromethyl)-4-aminophenyl)-1,4-phenylenediaminerepresented by the following Chemical Formula C was used instead ofdiamine DA2-1 prepared in Preparation Example 4.

EXAMPLE Example 1: Preparation of Liquid Crystal Alignment AgentComposition

According to the composition as shown in the following Table 1, 10 g ofthe polymer P-1 for a liquid crystal alignment agent prepared inSynthesis Example 1 and 10 g of the polymer Q-1 for a liquid crystalalignment agent prepared in Synthesis Example 5 were added to 12.4 g ofNMP and 7.6 g of n-butoxyethanol (a weight ratio of 8:2) to prepare a 5wt % solution. The obtained solution was filtered through apoly(tetrafluoroethylene) filter having a pore size of 0.1 μm underpressure to prepare a liquid crystal alignment agent composition.

Example 2: Preparation of Liquid Crystal Alignment Agent Composition

According to the composition as shown in the following Table 1, a liquidcrystal alignment agent composition was prepared in the same manner asin Example 1, except that the polymer P-3 for a liquid crystal alignmentagent was used instead of the polymer P-1 for a liquid crystal alignmentagent.

Example 3: Preparation of Liquid Crystal Alignment Agent Composition

According to the composition as shown in the following Table 1, a liquidcrystal alignment agent composition was prepared in the same manner asin Example 1, except that the polymer P-4 for a liquid crystal alignmentagent was used instead of the polymer P-1 for a liquid crystal alignmentagent.

Examples 4 to 23: Preparation of Liquid Crystal Alignment AgentCompositions

According to the composition as shown in the following Table 1, eachliquid crystal alignment agent composition was prepared in the samemanner as in Example 1, except that each of the polymers Q-2 to Q-21 fora liquid crystal alignment agent was used instead of the polymer Q-1 fora liquid crystal alignment agent.

Example 24: Preparation of Liquid Crystal Alignment Agent Composition

According to the composition as shown in the following Table 1, a liquidcrystal alignment agent composition was prepared in the same manner asin Example 1, except that the polymer P-2 for a liquid crystal alignmentagent prepared in Synthesis Example 2 was used instead of the polymerP-1 for a liquid crystal alignment agent, and the polymer Q-4 for aliquid crystal alignment agent was used instead of the polymer Q-1 for aliquid crystal alignment agent.

Examples 25 to 27: Preparation of Liquid Crystal Alignment AgentCompositions

According to the composition as shown in the following Table 1, eachliquid crystal alignment agent composition was prepared in the samemanner as in Example 24, except that each of the polymers Q-10 to Q-12for a liquid crystal alignment agent was used instead of the polymer Q-4for a liquid crystal alignment agent.

Example 28: Preparation of Liquid Crystal Alignment Agent Composition

According to the composition as shown in the following Table 1, a liquidcrystal alignment agent composition was prepared in the same manner asin Example 24, except that 4 g of the polymer P-2 for a liquid crystalalignment agent and 16 g of the polymer Q-4 for a liquid crystalalignment agent were added.

Examples 29 to 31: Preparation of Liquid Crystal Alignment AgentCompositions

According to the composition as shown in the following Table 1, eachliquid crystal alignment agent composition was prepared in the samemanner as in Example 28, except that each of the polymers Q-10 to Q-12for a liquid crystal alignment agent was used instead of the polymer Q-4for a liquid crystal alignment agent.

Comparative Example 1: Preparation of Liquid Crystal Alignment AgentComposition

A liquid crystal alignment agent composition was prepared in the samemanner as in Example 1, except that 20 g of the polymer P-1 for a liquidcrystal alignment agent was added without using the polymer Q-1 for aliquid crystal alignment agent.

Comparative Example 2: Preparation of Liquid Crystal Alignment AgentComposition

A liquid crystal alignment agent composition was prepared in the samemanner as in Example 1, except that 20 g of the polymer Q-1 for a liquidcrystal alignment agent was added without using the polymer P-1 for aliquid crystal alignment agent.

Comparative Example 3: Preparation of Liquid Crystal Alignment AgentComposition

According to the composition as shown in the following Table 1, a liquidcrystal alignment agent composition was prepared in the same manner asin Example 1, except that the polymer PR-1 for a liquid crystalalignment agent was used instead of the polymer P-1 for a liquid crystalalignment agent.

Comparative Examples 4 to 6: Preparation of Liquid Crystal AlignmentAgent Compositions

According to the composition as shown in the following Table 1, eachliquid crystal alignment agent composition was prepared in the samemanner as in Example 1, except that each of the polymers QR-1 to QR-3for a liquid crystal alignment agent was used instead of the polymer Q-1for a liquid crystal alignment agent.

Comparative Example 7: Preparation of Liquid Crystal Alignment AgentComposition

According to the composition as shown in the following Table 1, a liquidcrystal alignment agent composition was prepared in the same manner asin Comparative Example 5, except that the polymer P-3 for a liquidcrystal alignment agent was used instead of the polymer P-1 for a liquidcrystal alignment agent.

Comparative Example 8: Preparation of Liquid Crystal Alignment AgentComposition

According to the composition as shown in the following Table 1, a liquidcrystal alignment agent composition was prepared in the same manner asin Comparative Example 6, except that the polymer P-4 for a liquidcrystal alignment agent was used instead of the polymer P-1 for a liquidcrystal alignment agent.

Comparative Examples 9 to 11: Preparation of Liquid Crystal AlignmentAgent Compositions

According to the composition as shown in the following Table 1, eachliquid crystal alignment agent composition was prepared in the samemanner as in Example 1, except that each of the polymers S-1 to S-3 fora liquid crystal alignment agent was used instead of the polymer Q-1 fora liquid crystal alignment agent.

The polymer compositions of the liquid crystal alignment agentcompositions according to Examples 1 to 31 and Comparative Examples 1 to11 are as shown in the following Table 1.

TABLE 1 First polymer Second polymer Mixing weight ratio of Input Inputfirst and second Type (g) Type (g) polymers Example 1 P-1 10 Q-1 1050:50 Example 2 P-3 10 Q-1 10 50:50 Example 3 P-4 10 Q-1 10 50:50Example 4 P-1 10 Q-2 10 50:50 Example 5 P-1 10 Q-3 10 50:50 Example 6P-1 10 Q-4 10 50:50 Example 7 P-1 10 Q-5 10 50:50 Example 8 P-1 10 Q-610 50:50 Example 9 P-1 10 Q-7 10 50:50 Example 10 P-1 10 Q-8 10 50:50Example 11 P-1 10 Q-9 10 50:50 Example 12 P-1 10 Q-10 10 50:50 Example13 P-1 10 Q-11 10 50:50 Example 14 P-1 10 Q-12 10 50:50 Example 15 P-110 Q-13 10 50:50 Example 16 P-1 10 Q-14 10 50:50 Example 17 P-1 10 Q-1510 50:50 Example 18 P-1 10 Q-16 10 50:50 Example 19 P-1 10 Q-17 10 50:50Example 20 P-1 10 Q-18 10 50:50 Example 21 P-1 10 Q-19 10 50:50 Example22 P-1 10 Q-20 10 50:50 Example 23 P-1 10 Q-21 10 50:50 Example 24 P-210 Q-4 10 50:50 Example 25 P-2 10 Q-10 10 50:50 Example 26 P-2 10 Q-1110 50:50 Example 27 P-2 10 Q-12 10 50:50 Example 28 P-2 4 Q-4 16 20:80Example 29 P-2 4 Q-10 16 20:80 Example 30 P-2 4 Q-11 16 20:80 Example 31P-2 4 Q-12 16 20:80 Comparative P-1 20 — — 100:0  Example 1 Comparative— — Q-1 20  0:100 Example 2 Comparative PR-1 10 Q-1 10 50:50 Example 3Comparative P-1 10 QR-1 10 50:50 Example 4 Comparative P-1 10 QR-2 1050:50 Example 5 Comparative P-1 10 QR-3 10 50:50 Example 6 ComparativeP-3 10 QR-2 10 50:50 Example 7 Comparative P-4 10 QR-3 10 50:50 Example8 Comparative P-1 10 S-1 10 50:50 Example 9 Comparative P-1 10 S-2 1050:50 Example 10 Comparative P-1 10 S-3 10 50:50 Example 11

Experimental Example

1) Preparation of Liquid Crystal Alignment Cell

Each of the liquid crystal alignment agent compositions prepared in theexamples and comparative examples was used to prepare a liquid crystalalignment cell.

Specifically, the liquid crystal alignment agent composition was coatedonto the upper and lower substrates for a voltage holding ratio (VHR),in which ITO electrodes with a thickness of 60 nm and an area of 1 cm×1cm were patterned on a square glass substrate with a size of 2.5 cm×2.7cm, by a spin coating method, respectively. Then, the substrates coatedwith the liquid crystal alignment agent were placed on a hot plate atabout 70° C. and dried for 3 minutes to evaporate the solvent. Foralignment treatment of the coated substrates thus obtained, each ofupper and lower coated substrates was irradiated with UV at 254 nm underan exposure dose of 0.1 to 1.0 J/cm² using an exposure equipped with aline polarizer. Thereafter, the alignment-treated upper and lowersubstrates were baked (cured) in an oven at about 230° C. for about 30minutes to obtain a coating film with a thickness of 0.1 μm. Thereafter,a sealing agent impregnated with ball spacers with a size of 4.5 μm wascoated onto the edges of the upper substrate excluding a liquid crystalinlet. The alignment films formed on the upper and lower substrates werethen aligned such that they faced each other and the alignmentdirections were aligned with each other, and the upper and lowersubstrates were bonded together and the sealing agent was cured with UVand heat to prepare an empty cell. Then, a liquid crystal was injectedinto the empty cells, and the inlet was sealed with a sealing agent toprepare a liquid crystal cell.

2) Evaluation of Liquid Crystal Alignment Property

Polarizing plates were attached to the upper and lower substrate platesof the above-prepared liquid crystal cell so as to be perpendicular toeach other. At this time, the polarizing axis of the polarizing plateattached to the lower substrate plate was allowed to be parallel to thealignment axis of the liquid crystal cell. The polarizing plate-attachedliquid crystal cell was placed on a backlight having luminance of 7000cd/cm², and light leakage was observed with the naked eye. When theliquid crystal alignment film had an excellent alignment property toalign liquid crystals properly, light did not pass through the upper andlower polarizing plates which were attached perpendicular to each other,and the liquid crystal cell was observed dark without defects. In thiscase, the alignment property was recorded as ‘good’. When light leakagesuch as a liquid crystal flow mark or a bright spot was observed, it wasrecorded as ‘poor’ in Table 2 below.

3) Evaluation of Liquid Crystal Alignment Stability

Polarizing plates were attached to the upper and lower substrate platesof the above-prepared liquid crystal alignment cell so as to beperpendicular to each other. The polarizing plate-attached liquidcrystal alignment cell was attached on a backlight having luminance of7000 cd/cm², and the luminance in a black state was measured using aluminance measuring instrument PR-880. Then, the liquid crystal cell wasoperated at room temperature with an alternating voltage of 5 V for 24hours. Thereafter, in the voltage-off state of the liquid crystal cell,luminance in the black state was measured as described above. Adifference between the initial luminance (L₀) measured before operationof the liquid crystal cell and the later luminance (L₁) measured afteroperation was divided by the initial luminance (L₀), and then multipliedby 100 to calculate a luminance fluctuation rate. As the calculatedluminance fluctuation rate is close to 0%, it means that the alignmentstability is excellent. Through the measurement results of the luminancefluctuation rate, the afterimage level was evaluated under the followingcriteria. It is preferable that the AC afterimage is minimized. In themeasurement results, when the luminance fluctuation rate was less than10%, it was evaluated as ‘excellent’, when the luminance fluctuationrate was between 10% to 20%, it was evaluated as ‘ordinary’, and whenthe luminance fluctuation rate was more than 20%, it was evaluated as‘poor’. The results are shown in Table 2 below.

4) Measurement of Voltage Holding Ratio (VHR)

Liquid crystal cells for voltage holding ratio were prepared using theliquid crystal alignment agents prepared in Examples 1 to 31 andComparative Examples 1 to 11 by the following method, respectively.

The liquid crystal alignment agent was coated onto the upper and lowersubstrates for a voltage holding ratio (VHR), in which ITO electrodeswith a thickness of 60 nm and an area of 1 cm×1 cm were patterned on asquare glass substrate with a size of 2.5 cm×2.7 cm, by a spin coatingmethod, respectively.

Then, the substrates coated with the liquid crystal alignment agent wereplaced on a hot plate at about 70° C. and dried for 3 minutes toevaporate the solvent. For alignment treatment of the coated substratesthus obtained, each of upper and lower coated substrates was irradiatedwith UV at 254 nm under an exposure dose of 1 J/cm² using an exposureequipped with a line polarizer. Thereafter, the alignment-treated upperand lower substrates were baked and cured in an oven at about 230° C.for 30 minutes to obtain a coating film with a thickness of 0.1 μm.Thereafter, a sealing agent impregnated with ball spacers with a size of4.5 μm was coated onto the edges of the upper/lower substrate excludinga liquid crystal inlet. The alignment films formed on the upper andlower substrates were then aligned such that they faced each other andthe alignment directions were aligned with each other, and the upper andlower substrates were bonded together and the sealing agent was curedwith UV and heat to prepare an empty cell. Then, a liquid crystal wasinjected into the empty cells, and the inlet was sealed with a sealingagent to prepare a liquid crystal cell.

The voltage holding ratio (VHR) which is an electrical property of theliquid crystal cell prepared by the above method was measured using TOYO6254 equipment. The voltage holding ratio was measured under harshconditions of 1 V, 1 Hz, and 60° C. The voltage holding ratio of 100% isan ideal value. When the measurement result is 70% or more, it isevaluated as ‘good’, and when the measurement result is less than 70%,it is evaluated as ‘poor’, and the results are shown in Table 2 below.

TABLE 2 Evaluation of Evaluation of Evaluation of liquid crystal liquidcrystal voltage holding alignment property alignment stability ratioExample 1 Good Excellent Good Example 2 Good Excellent Good Example 3Good Excellent Good Example 4 Good Excellent Good Example 5 GoodExcellent Good Example 6 Good Excellent Good Example 7 Good ExcellentGood Example 8 Good Excellent Good Example 9 Good Excellent Good Example10 Good Excellent Good Example 11 Good Excellent Good Example 12 GoodExcellent Good Example 13 Good Excellent Good Example 14 Good ExcellentGood Example 15 Good Excellent Good Example 16 Good Excellent GoodExample 17 Good Excellent Good Example 18 Good Excellent Good Example 19Good Excellent Good Example 20 Good Excellent Good Example 21 GoodExcellent Good Example 22 Good Excellent Good Example 23 Good ExcellentGood Example 24 Good Excellent Good Example 25 Good Excellent GoodExample 26 Good Excellent Good Example 27 Good Excellent Good Example 28Good Excellent Good Example 29 Good Excellent Good Example 30 GoodExcellent Good Example 31 Good Excellent Good Comparative Good OrdinaryPoor Example 1 Comparative Poor Poor Good Example 2 Comparative PoorPoor Poor Example 3 Comparative Good Good Poor Example 4 ComparativeGood Good Poor Example 5 Comparative Good Good Poor Example 6Comparative Good Good Poor Example 7 Comparative Good Good Poor Example8 Comparative Poor Poor Good Example 9 Comparative Good Ordinary GoodExample 10 Comparative Poor Poor Poor Example 11 * Light exposure doseduring production of liquid crystal alignment cell: 0.1 to 1.0 J/cm²

As shown in Table 2, it was confirmed that since each of the liquidcrystal alignment agent compositions of Examples 1 to 31 includes thepolymer for the first liquid crystal alignment agent which is apartially imidized polyimide precursor along with the polymer for thesecond liquid crystal alignment agent which is a polyimide precursorderived from a diamine having an asymmetric pyridine structure, anexcellent alignment property may be obtained without an initialthermosetting process, the AC afterimage-related luminance fluctuationrate was excellent at less than 10%, and the voltage holding ratio wasalso excellent at 70% or more under a high temperature environment,thereby exhibiting excellent effects in terms of electrical properties.

In contrast, the liquid crystal alignment agent compositions ofComparative Examples 1 to 11 include neither of the polymer for thefirst liquid crystal alignment agent which is a partially imidizedpolyimide precursor or the polymer for the second liquid crystalalignment agent which is a polyimide precursor derived from a diaminehaving an asymmetric pyridine structure or include only the polymercomposed of the single component of the diamines, and as a result,electrical properties or alignment properties of the liquid crystalcells were remarkably deteriorated.

Particularly, in the case of Comparative Example 1, only the polymer forthe first liquid crystal alignment agent which is a partially imidizedpolyimide precursor was used, and as a result, there was no problem inthe alignment property of the liquid crystal alignment film, but the ACafterimage-related luminance fluctuation rate was 10% or more, and thusdeterioration in the liquid crystal alignment stability was observed. Inaddition, the voltage holding ratio was less than 70%, which wasevaluated as ‘poor’. In the case of Comparative Example 2, only thepolymer for the second liquid crystal alignment agent which is apolyimide precursor derived from a diamine having an asymmetric pyridinestructure was used. As a result, the voltage holding ratio was observedat the equivalent level or more, but there were problems in that lightleakage such as a liquid crystal flow mark or a bright spot was observedin the evaluation of the alignment property of the liquid crystalalignment film, and thus it was evaluated as ‘poor’, and the luminancefluctuation rate of more than 20% was observed in the AC afterimageevaluation, and thus it was evaluated as ‘poor’. In the case ofComparative Example 3, the polymer for the second liquid crystalalignment agent which is a polyimide precursor derived from a diaminehaving an asymmetric pyridine structure was used, butpara-phenylenediamine (p-PDA) was used instead of the partially imidizedpolyimide precursor as the first liquid crystal polymer, and as aresult, all of the liquid crystal alignment property, stability, andvoltage holding ratio were evaluated as ‘poor’.

Furthermore, in the case of Comparative Examples 4 to 11, the polymerfor the first liquid crystal alignment agent which is the partiallyimidized polyimide precursor was used, but the polymer prepared usingpara-phenylenediamine (p-PDA), oxydianiline (ODA), or methylenedianiline(MDA) was used instead of the diamine having the specific asymmetricstructure which is the polymer for the second liquid crystal alignmentagent, and as a result, there was no problem in the liquid crystalalignment property, but their voltage holding ratio was less than 70%,and thus they were evaluated as ‘poor’, indicating that there is aproblem in terms of electrical properties.

The invention claimed is:
 1. A liquid crystal alignment film comprisinga liquid crystal alignment agent composition comprising a first polymerfor a first liquid crystal alignment agent including a repeating unitrepresented by Chemical Formula 1 and one or more repeating unitsselected from the group of a repeating unit represented by ChemicalFormula 2 and a repeating unit represented by Chemical Formula 3,wherein the repeating unit represented by Chemical Formula 1 is includedin an amount of 5 mol % to 74 mol % with respect to a total of therepeating units represented by the following Chemical Formulae 1 to 3;and a second polymer for a second liquid crystal alignment agentincluding one or more repeating units selected from the group of arepeating unit represented by Chemical Formula 4, a repeating unitrepresented by Chemical Formula 5, and a repeating unit represented byChemical Formula 6:

wherein, in the Chemical Formulae 1 to 6, R¹, R², R³, and R⁴ are eachindependently hydrogen or a C₁₋₁₀ alkyl, provided that R¹ and R² are notboth hydrogen, and that R³ and R⁴ are not both hydrogen, X¹ is atetravalent organic group represented by Chemical Formula 7:

wherein, in the Chemical Formula 7, R⁵, R⁶, R⁷, and R⁸ are eachindependently hydrogen or a C₁₋₆ alkyl, X², X³, X⁴, X⁵, and X⁶ are eachindependently a tetravalent organic group derived from a hydrocarbonhaving 4 to 20 carbon atoms, or a tetravalent organic group derived froma hydrocarbon having 4 to 20 carbon atoms wherein one or more of H issubstituted with a halogen, or one or more of —CH₂— is substituted with—O—, —CO—, —S—, —SO—, —SO₂—, or —CONH— to prevent direct binding withoxygen or sulfur atoms in the tetravalent organic group, in the ChemicalFormulae 1 to 3, Y¹ to Y³ are each independently a divalent organicgroup represented by Chemical Formula 8:

wherein, in the Chemical Formula 8, R⁹ and R¹⁰ are each independently ahalogen, a cyano, a C₁₋₁₀ alkyl, a C₂₋₁₀ alkenyl, a C₁₋₁₀ alkoxy, aC₁₋₁₀ fluoroalkyl, or a C₁₋₁₀ fluoroalkoxy, p and q are eachindependently an integer of 0 to 4, L¹ is a single bond, —O—, —CO—, —S—,—SO₂—, —C(CH₃)₂—, —C(CF₃)₂—, —CONH—, —COO—, —(CH₂)_(z)—, —O(CH₂)_(z)O—,—O (CH₂)_(z)—, —OCH₂—C(CH₃)₂—CH₂O—, —COO—(CH₂)_(z)—OCO—, or—OCO—(CH₂)_(z)—COO—, wherein z is an integer of 1 to 10, k and m areeach independently an integer of 1 to 3, n is an integer of 0 to 3, inChemical the Formulae 4 to 6, Z¹, Z², and Z³ are each independently adivalent organic group represented by Chemical Formula 9:

wherein, in the Chemical Formula 9, A¹ is an element of nitrogen,phosphorus, arsenic, tin or bismuth, R¹¹ is hydrogen or a C₁₋₁₀ alkyl, ais an integer of 1 to 3, and A², A³, A⁴, and A⁵ are nitrogen or carbon,provided that at least one of A² or A⁵ is nitrogen and the other iscarbon and A³ and A⁴ are carbon, wherein X2, X3, X4, X5, and X6 are eachindependently a tetravalent organic group represented by ChemicalFormula 10: [Chemical Formula 10]

wherein, in Chemical Formula 10, R⁵, R⁶, R⁷, and R⁸ are eachindependently hydrogen or a C₁₋₆ alkyl, R¹² and R¹³ are eachindependently hydrogen or a C₁₋₁₀ alkyl, and L² is any one selected fromthe group consisting of a single bond, —O—, —CO—, —S—, —SO—, —SO₂—,—CR¹⁴R¹⁵—, —CONH—, —COO—, —(CH₂)_(b)—, —O—(CH₂)_(b)O—,—COO—(CH₂)_(b)—OCO—, —HN—(CH₂)_(b)—NH—, —R¹⁴N—(CH₂)_(b)—NR¹⁵—,phenylene, and combinations thereof, wherein R¹⁴ and R¹⁵ are eachindependently hydrogen, a C₁₋₁₀ alkyl, or a C₁₋₁₀ fluoroalkyl, and eachb is independently an integer of 1 to 10, wherein, Y¹ of the repeatingunit represented by Chemical Formula 1 is connected to an adjacentrepeating unit represented by Chemical Formula 1 as N—Y¹—N—, or to anadjacent repeating unit represented by Chemical Formula 2 or 3 as—HN—Y¹—N—; Y² of the repeating unit represented by Chemical Formula 2 isconnected to an adjacent repeating unit represented by Chemical Formula2 or 3 as —HN—Y²—NH—, or to an adjacent repeating unit represented byChemical Formula 1 as —N—Y²—NH—; and Y³ of the repeating unitrepresented by Chemical Formula 3 is connected to an adjacent repeatingunit represented by Chemical Formula 2 or 3 as —NH—Y³—NH— or to anadjacent repeating unit represented by Chemical Formula 1 as —N—Y³—NH—,wherein, Z¹ of the repeating unit represented by Chemical Formula 4 isconnected to an adjacent repeating unit represented by Chemical Formula4 as —N—Z¹—N—, or to an adjacent repeating unit represented by ChemicalFormula 5 or 6 as —HN—Z¹—N—; Z² of the repeating unit represented byChemical Formula 5 is connected to an adjacent repeating unitrepresented by Chemical Formula 5 or 6 as —HN—Z²—NH—, or to an adjacentrepeating unit represented by Chemical Formula 4 as —N—Z²—NH—; and Z³ ofthe repeating unit represented by Chemical Formula 6 is connected to anadjacent repeating unit represented by Chemical Formula 5 or 6 as—NH—Z³—NH— or to an adjacent repeating unit represented by ChemicalFormula 4 as —N—Z³—NH—, and wherein the liquid crystal alignment film isprepared by an alignment treatment including irradiating with polarizedlight or rubbing in one direction, without preceding or concurrentcuring, prior to a curing heat treatment.
 2. The liquid crystalalignment agent film of claim 1, wherein the Chemical Formula 8 is adivalent organic group represented by Chemical Formula 11 or ChemicalFormula 12:

wherein, in Chemical Formula 12, L³ is a single bond, —O—, —SO₂—, or—CR¹⁶R¹⁷—, wherein R¹⁶ and R¹⁷ are each independently hydrogen or aC₁₋₁₀ alkyl.
 3. The liquid crystal alignment agent film of claim 1,wherein in the Chemical Formula 9, A¹ is nitrogen, R¹¹ is hydrogen, anda is
 1. 4. The liquid crystal alignment agent film of claim 1, whereinthe Chemical Formula 9 includes one or more repeating units selectedfrom the group of Chemical Formula 9-1, Chemical Formula 9-2, andChemical Formula 9-3:

wherein, in the Chemical Formulae 9-1 to 9-3, A¹ to A⁵, R¹¹, and a areas defined in claim
 1. 5. The liquid crystal alignment agent film ofclaim 1, wherein the first polymer for the first liquid crystalalignment agent and the second polymer for the second liquid crystalalignment agent are included at a weight ratio of 5:95 to 95:5.
 6. Theliquid crystal alignment agent film of claim 1, wherein the secondpolymer for the second liquid crystal alignment agent further includesone or more repeating units selected from the group of a repeating unitrepresented by Chemical Formula 13, a repeating unit represented byChemical Formula 14, and a repeating unit represented by ChemicalFormula 15:

wherein, in the Chemical Formulae 13 to 15, at least one of R¹⁸ and R¹⁹is an alkyl group having 1 to 10 carbon atoms and the other is hydrogen,X⁷ to X⁹ are each independently a tetravalent organic group, and Z⁴ toZ⁶ are each independently a divalent organic group represented byChemical Formula 16:

wherein, in the Chemical Formula 16, R²⁰ and R²¹ are each independentlya halogen, a cyano, a C₁₋₁₀ alkyl, a C₂₋₁₀ alkenyl, a C₁₋₁₀ alkoxy, aC₁₋₁₀ fluoroalkyl, or a C₁₋₁₀ fluoroalkoxy, p′ and q′ are eachindependently an integer of 0 to 4, L⁴ is a single bond, —O—, —CO—, —S—,—SO₂—, —C(CH₃)₂—, —C(CF₃)₂—, —CONH—, —COO—, —(CH₂)_(z)—, —O (CH₂)_(z)O—,—O (CH₂)_(z)—, —OCH₂—C(CH₃)₂—CH₂O—, —COO—(CH₂)_(z)—OCO—, or—OCO—(CH₂)_(z)—COO—, wherein each z is independently an integer of 1 to10, k′ and m′ are each independently an integer of 0 to 3, n′ is aninteger of 0 to 3, and when n′=0, k′ is 1 to 3, and when k′=0, m and nare each independently 1 to
 3. 7. The liquid crystal alignment agentfilm of claim 6, wherein the Chemical Formula 16 is Chemical Formula 17or Chemical Formula 18:

wherein, in the Chemical Formula 18, L⁵ is a single bond, —O—, —SO₂—, or—CR²²R²³—, wherein R²² and R²³ are each independently hydrogen or aC₁₋₁₀ alkyl.
 8. A method of producing the liquid crystal alignment filmof claim 1, the method comprising the steps of: coating a solution or adispersion, of the liquid crystal alignment agent composition comprisingthe first polymer for a first liquid crystal alignment agent and thesecond polymer for a second liquid crystal alignment agent onto asubstrate to form a coating film; drying the coating film; irradiatingthe coating film with light immediately after the step of drying thecoating film to perform an alignment treatment; and heat-treating andcuring the alignment-treated coating film.
 9. The method of producingthe liquid crystal alignment film of claim 8, wherein the liquid crystalalignment agent composition is dissolved or dispersed in an organicsolvent.
 10. The method of producing the liquid crystal alignment filmof claim 8, wherein the step of drying the coating film is performed at50° C. to 150° C.
 11. The method of producing the liquid crystalalignment film of claim 8, wherein in the alignment treatment step, thelight irradiation is performed by irradiating polarized ultraviolet rayshaving a wavelength of 150 nm to 450 nm.
 12. The method of producing theliquid crystal alignment film of claim 8, wherein in the step ofheat-treating and curing the coating film, the heat treatmenttemperature is 150° C. to 300° C.
 13. A liquid crystal display devicecomprising the liquid crystal alignment film of claim 1.